Monday, August 4, 2014

Goalkeepers prone to 'gambler's fallacy' but penalty takers fail to exploit it

After a string of penalties aimed in the same direction, goalkeepers are more likely to dive in the opposite direction on the next penalty

After a string of penalties aimed in the same direction, goalkeepers are more likely to dive in the opposite direction on the next penalty but kickers fail to exploit this pattern, finds new UCL research.
The study, published in Current Biology, shows that penalty shoot-outs in international tournaments resemble a psychological game. The researchers studied penalty shoot-out videos from all World Cup and Euro finals tournaments between 1976 and 2012.
They found that each team of kickers produced more or less random sequences of kicks to the left or the right of the goal. Goalkeepers' dives to the left or the right were not related to the direction of the kick, suggesting that goalkeepers at this elite level make their decisions in advance, rather than reacting to each kick. However, goalkeepers' decisions were non-random in one crucial respect: when the kickers repeatedly kicked in the same direction on consecutive penalties, goalkeepers became more likely to dive in the opposite direction on the next penalty. The goalkeepers therefore display what has been called the 'gambler's fallacy' – like a person who believes that after coin flips produce a run of 'heads', the next flip is bound to produce 'tails'.
"Complete randomness is generally the best strategy in competitive games" says lead author Erman Misirlisoy of the UCL Institute of Cognitive Neuroscience. "Because the goalkeeper displays the gambler's fallacy, kickers could predict which way the goalkeeper is likely to dive on the next kick. That would obviously give the kicker an advantage – they would simply aim for the opposite side of the goal. Surprisingly, though, we found that kickers failed to exploit this advantage".
"Often you can only win in elite sport by exploiting tiny weaknesses in your opponent's strategy", explains senior author Professor Patrick Haggard. "We can only speculate on why goalkeepers can get away with non-randomness, without the kickers exploiting it. One possibility is that penalty shoot-outs are relatively rare. But there is a more psychologically interesting possibility: shoot-outs are asymmetric, because one goalkeeper faces several different kickers, one after the other. Kickers are under enormous pressure, focussed on the moment of their own kick. Each individual kicker may not pay enough attention to the sequence of preceding kicks to predict what the goalkeeper will do next."
Erman Misirlisoy adds: "People can learn to predict: perhaps football coaches could study the gambler's fallacy, and could train their penalty kickers in preparation for the next World Cup. At the same time, goalkeepers could also learn to be less predictable".

Friday, June 6, 2014

Physics experts: Soccer ball created for the 2014 FIFA World Cup is a “keepers’ ball”.

New Ball to Showcase Talent in World CupUniversity of Adelaide

The new ball, called Brazuca, should be much more predictable than the 2010 World Cup ball, Jabulani, which was less-than-affectionately labelled a ‘beach ball’ because of its sometimes erratic flight path.
“The Brazuca has very deep grooves – it’s much rougher than Jabulani – and this creates a different pattern of air flow around the ball,” says Professor Derek Leinweber, Professor of Physics in the University’s School of Chemistry and Physics. He has previously written about and lectured on the aerodynamics of cricket balls, golf balls and earlier World Cup soccer balls.
“The Jabulani was much smoother than the Brazuca with smaller grooves and ridges across its surface,” says Professor Leinweber. “That meant the ball had to be moving much faster before the airflow around the ball changed from smooth to turbulent. As this shift to turbulent airflow occurred at high speeds, the ball could make some pretty erratic movements on the way to the net.
“In contrast the Brazuca, with its deeper grooves, hits that turbulent air flow at a lower speed with the result that the ball is much more predictable. In many ways, it’s a return to the aerodynamics of the old 32-panel ball.”
Professor Leinweber and PhD candidate Adrian Kiratidis have been investigating the likely performance of the new ball by matching up the physics of air flow with available wind tunnel data and video of the ball’s movement.
Mr Kiratidis says he believes players taking hard and fast shots in this World Cup won’t find the Brazuca as easy to bend into the net as they did with the Jabulani.
“Keepers facing players of the calibre of Messi, Cristiano Ronaldo or Neymar are going to be glad that it’s Brazuca coming at them rather than Jabulani,” he says.
Mr Kiratidis will explain the science behind World Cup soccer balls at a free public lecture on Thursday 12 June at 6.30pm, just hours before the first kick-off in Brazil.
The lecture, The Brazuca – a better ball?, will be held at 6.30-7.30pm, Lecture Theatre 102, Napier Building, at the University’s North Terrace campus.
Commentary from Professor Leinweber and Adrian Kiratidis on the Brazuca is available on the YouTube video at

Friday, March 21, 2014

Female soccer players get tired more, run hard less

Every year billions of people across the globe tune in to watch the UEFA Champions League in which men compete, yet the number who tune-in to watch the female equivalent is miniscule and research carried out at a North East University has discovered it is a whole different ball game.

For the first time both versions of the sport have been compared by the University of Sunderland to discover how the male game differs from that of the female game from a physical and technical point of view.

Research published in the journal Human Movement Science analysed 54 male and 59 female football (soccer) player observations in the UEFA Champions League. It is the first study to focus on high-intensity running in football for both men and women.

They found that during the course of a typical UEFA Champions League match male players covered approximately 3-5 per cent more distance in total than females but covered around 30 per cent more distance at high intensity. The research also showed female players did not cover as much distance in the second half at a high intensity as they did in the first half, while male players did manage to maintain their running performances.

There were no gender differences shown between attackers and central defenders; however male full-backs, central and wide midfielders covered more distance at high intensity compared to female players in the same position.

The research, 'Gender differences in match performance characteristics of soccer players', also showed the difference in technical characteristics with female players losing the ball more frequently and having a lower pass completion rate.

Dr Paul Bradley, led the research and is a Senior Lecturer in Sport and Exercise Science at the University of Sunderland. He said: "We can clearly see that the male and female game at the top level is very different both physically and technically. It was very interesting to see fairly similar total distances but substantial differences at high intensity between gender. The larger drop off in running performance in the second half for females could be due and their lower physical capacity thus, the demands of the game cause fatigue in the second half."

It is now hoped the research can be used to provide gender-specific training for professionals in both male and female footballers to improve physical and technical performance.

Tuesday, March 11, 2014

MLB pitchers don't regain performance level after Tommy John surgery

     Major League Baseball players who undergo Tommy John surgery are less likely to regain the performance level they had before surgery, according to a Henry Ford Hospital study.

The study is the first to show a link between the surgery and declining pitching performance at the professional level. It also involved the largest cohort of professional pitchers to date to examine the issue.

Researchers analyzed pitching statistics of 168 MLB pitchers before and after surgery between 1982 and 2010 and found diminishing returns in three major pitching categories: Earned runs average (ERA), walks and hits per inning pitched (WHIP) and innings pitched (IP). The findings:

ERA increased 4.15 to 4.74.
WHIP increased 1.40 to 1.48.
IP declined 59 to 50.

"Tommy John surgery is an effective surgery and most pitchers get back to pitching after surgery. But it's not going to improve their level of performance," says Vasilios (Bill) Moutzouros, M.D., a Henry Ford orthopedic surgeon and the study's senior author.

"There's been a perception that the surgery will make you better. Our findings debunk that perception. Eighty to 90 percent of major league pitchers will get back to pitching at the major league level but they just won't be as effective as they were before injury."

The study is being presented at the annual meeting of the American Academy of Orthopedic Surgeons March 11-15 in New Orleans.

Tommy John surgery, named after the former Los Angeles Dodgers pitcher who underwent the pioneering surgery 40 years ago, has been since performed on legions of pitchers at the professional and collegiate levels. In medicine it is known as ulnar collateral ligament (UCL) reconstruction. During the two-hour outpatient procedure, the ulnar collateral ligament in the medial elbow is replaced with a tendon from the same arm or from the hamstring area.


 IMAGE: This is Vasilios (Bill) Moutzouros, M.D., a Henry Ford Hospital orthopedic surgeon and study's senior author.
Click here for more information.

Until Henry Ford's observational study, other research had shown that a high percentage of players returned to the same level of performance after UCL reconstruction, and the perception among players, coaches and parents was that UCL reconstruction would even lead to a higher level of performance. In the only other study involving just MLB pitchers (68 pitchers), 82 percent of them returned to the mound after surgery and had no significant decline in performance.

Henry Ford researchers sought to examine the effects of UCL reconstruction on pitching performance involving the largest cohort of MLB pitchers and identify risk factors associated with the pitching injury, says Robert Keller, M.D., a third-year Henry Ford orthopedic resident and study co-author whose father Phil was a teammate of Tommy John in the 1970s.

The cohort of 168 pitchers pitched in at least major league game after undergoing UCL reconstruction between 1982 and 2010. Data collected included the year of surgery, pitchers' age, years of MLB experience, height/weight, body mass index, pitching arm injured, pitching role, pitching statistics, and whether the pitcher returned to MLB pitching after surgery. This was then averaged for the three years of pitching before UCL reconstruction and for the three years after returning to play.

For comparison, researchers collected similar data of 178 MLB pitchers in a control group with no prior UCL reconstruction and age-matched them with a corresponding UCL reconstruction pitcher. Performance was determined using three years of statistics before their "index year" (their roster year of either 2004 or 2005) and three years after their "index year."

Drs. Moutzouros and Keller used paired analysis, generalized estimating equation model and other commonly used research tests to evaluate the data. Other highlights:

- UCL pitchers were "statistically better" than the control group in ERA, WHIP, IP and win percentage in the three years and two years before surgery.
- In the year before surgery, UCL pitchers' performance declined significantly.
- After surgery, the control group was either superior in nearly every performance measure or no difference observed.
- A predictor of surgery is MLB experience. Sixty percent of pitchers required UCL reconstruction within their first five years in the MLB.
- While the cause of UCL injury is not fully known, orthopedic specialists theorize it's due to overuse and stress on the elbow, pitching velocity and joint motion, Dr. Keller says, adding that surgery isn't a panacea.

"We even have parents who come into our clinic asking if their children can have the surgery even before they injure anything because they think potentially it can make them better. What this study shows is it doesn't. Matter of fact, players get statistically worse after having this surgery."

Study finds no greater soccer injury risk on artificial playing surfaces

New research presented today at the 2014 Annual Meeting of the American Academy of Orthopaedic Surgeons (AAOS) found no greater injury risk for athletes playing on artificial playing surfaces.

The use of artificial playing surfaces at sport venues has increased significantly in recent years, primarily due to the advantages of artificial turf over natural grass: longer playing hours, lower maintenance costs and greater resilience to harsh weather conditions. Despite these advantages, many elite professional soccer teams are reluctant to install artificial turf because of a perception that injuries occur more often on these types of surfaces.

In the study, "Safety of Third Generation Artificial Turf in Male Elite Professional Soccer Players," Italian researchers reviewed injuries involving players in the top Italian football (soccer) league during the 2011-2012 season.

A total of 2,580 hours of play were recorded (1,270 hours on artificial turf and 1,310 on grass). For every 1,000 hours of play there were 23 injuries recorded on artificial surfaces and 20 on grass, with muscle strains being the most common injury (13 on artificial turf, 14 on grass). The authors of the study do not consider the injury rates between the two surfaces to be statistically significant, as only three injuries per 1,000 hours of play were attributable to artificial surfaces.

The study authors concluded that there are no major differences between the nature and causes of injuries sustained on artificial turf and those that occur on natural grass surfaces.

Major League Baseball players win more games following Tommy John surgery

Since 1986, 83 percent of patients returned to professional play

Ulnar collateral ligament (UCLR) reconstruction, otherwise known as "Tommy John Surgery," is a procedure frequently performed on Major League Baseball (MLB) pitchers with a damaged or torn ulnar collateral ligament, a common elbow injury, typically from overuse.

In the new study, "Rate of Return to Pitching and Performance after Tommy John Surgery in Major League Baseball Pitchers," * presented today at the 2014 Annual Meeting of the American Academy of Orthopaedic Surgeons (AAOS), researchers looked at the rate of return to MLB pitching following UCLR, the level of performance in pitchers returning to MLB, and the difference in overall performance between pitchers who underwent UCLR and demographic-matched controls who did not. Researchers evaluated UCLR pitchers between 1986 and 2012 using a number of performance-based statistics and compared them with matched controls: age, body mass index (BMI), position, handedness and MLB experience.

In the year prior to surgery, the UCLR pitchers were outperformed by controls in terms of the number of innings pitched, games played and winning percentage. However, after undergoing UCLR, pitchers allowed significantly fewer walks and hits per inning pitched (WHIP), won a higher percentage of games, and recorded lower earned run averages (ERA) than prior to their surgeries. The UCLR pitchers also recorded higher winning percentages and lower WHIP and ERA in their post-surgical career than the control group. Overall, 83 percent of UCLR patients were able to return to MLB, and their careers on average lasted an additional 3.9 years.

The authors of the study concluded that there is a high rate of pitchers returning to MLB following UCLR, with a significant improvement in pitching performance.

Thursday, February 27, 2014

Disney Research soccer analysis suggests home advantage is result of strategy

An automated analysis by Disney Research Pittsburgh of team formations used during an entire season of professional soccer provides further evidence that visiting teams are less successful than home teams because they play conservatively, not because of a mythical home advantage.

The researchers, employing the first automated method for detecting formations, analyzed a whole season of player and ball tracking data compiled by Prozone for a top-tier professional soccer league. They found that teams usually played the same formations for both home and away games, but that the way they executed those formations was significantly different.

The players consistently played more forward up the field at home than they do on the road, both when attacking and defending. The home team thus is more likely to win the ball when it is in an advanced position, which can lead to more shots on goal.

"It also means that home teams actually run less, so they don't get as tired during the match," said Patrick Lucey, a Disney researcher specializing in automatic measurement of human behavior.

The researchers will present their findings at the MIT Sloan Sports Analytics Conference, Feb. 28-March 1 in Boston, MA.

The automated formation detection method developed by Disney Research also summarizes game information in a visual form.

According to Lucey, "You can think of it as a weather map that shows which team is dominating and the tactics that each team is using."

An earlier study by Lucey and his colleagues, which used ball action data compiled by Opta for a professional soccer league's season, showed that performance measures such as shooting and passing percentages were similar for home and visiting teams. But home teams more often had the ball in the forward third of the field, where players were in position to get more shots on goal. Lucey said it appeared visiting teams were playing "not to lose," rather than playing "to win," reflecting the common wisdom to "win at home and draw away."

The new study takes that analysis deeper, showing that the home/away differences are the result of how formations are executed, not different formations.

Recognizing player formations is relatively easy for human observers, but until now has been difficult for computerized methods, Lucey said. The Disney researchers, however, have found a way to account for players as they swap roles during the course of play.

While a team scout might be able to summarize the formations used in a game by an upcoming opponent, the computerized method enables detailed analysis of multiple games or an entire season of play – far more data than any human could make sense of. This formation analysis also can occur during a game, providing a tool that might help both coaches and broadcast commentators visualize team performance in real time.